Method of direct embedding a lithium ion battery on a flexible printed circuit board
A flexible printed circuit board with a lithium ion battery printed thereon is achieved. The flexible printed circuit board comprises a top and a bottom electrically insulating base film, a top electrically conductive metal layer over the top electrically insulating base film, and a bottom electrically conductive metal layer under the bottom electrically insulating base film. A printable lithium ion battery sits in a cavity completely through the top and bottom base films wherein a top of the battery contacts the top electrically conductive metal layer and wherein a bottom of the battery contacts the bottom electrically conductive metal layer. An adhesive film around the battery seals it to the top and bottom electrically insulating base film and seals the top electrically conductive metal layer to the bottom electrically conductive metal layer.
1. A flexible printed circuit board with a printable lithium ion battery directly printed thereon, comprising
a top and a bottom electrically insulating base film;
a top electrically conductive metal layer over said top electrically insulating base film and a bottom electrically conductive metal layer under said bottom electrically insulating base film,
a printable lithium ion battery in a cavity completely through said top and bottom base films wherein a top of said battery contacts said top electrically conductive metal layer and wherein a bottom of said battery contacts said bottom electrically conductive metal layer and wherein said lithium ion battery comprises:
an anode at said bottom of said battery,
an aluminum layer at said top of said battery;
a cathode underlying said aluminum layer; and
a solid state electrolyte between said anode and said cathode, wherein said aluminum layer is electrically connected to said top electrically conductive metal layer by a conductive adhesive; and
an adhesive film around said battery sealing it to said top and bottom electrically insulating base film and sealing said top electrically conductive metal layer to said bottom electrically conductive metal layer.
2. The flexible printed circuit board according to claim 1 wherein said top and bottom electrically insulating base films comprise two portions of a same said flexible printed circuit board, said top electrically insulating base film folded over said bottom electrically insulating base film with said printable lithium ion battery therebetween.
3. The flexible printed circuit board according to claim 1 , further comprising surface finishing on said top and bottom electrically conductive metal layers to provide high resistance to water and oxygen wherein said surface finishing comprises nickel, palladium, gold, tin, silver, aluminum, or ruthenium or a combination of thereof.
4. The flexible printed circuit board according to claim 1 , wherein said top and bottom base film comprises polyimide (PI), liquid crystal polymer (LCP), Cyclo-olefin polymer (COP), polyester (PET), polyethylene-naphtalate (PEN), poly tetra fluoro ethylene, or laminate substrate such as epoxies and BT, or Teflon, or modified Teflon having a thickness of between about 10 and 50 μm.
5. The flexible printed circuit board according to claim 1 , wherein said top and bottom metal layers comprise copper having a thickness of between about 5 and 50 μm.
6. The flexible printed circuit board according to claim 3 , wherein the combination of electrically insulating base film and metal layer with surface finishing has a water vapor absorption rate no higher than 1×10 −3 g m −2 per day.
7. The flexible printed circuit board according to claim 1 , wherein said top and bottom metal layers work as current collectors and positive and negative terminals of said battery by connecting with electrical conductive metal traces of said positive and negative terminals.
8. The flexible printed circuit board according to claim 1 wherein no external connection or electrical contact is needed to connect said flexible printed circuit board and said battery.
9. The flexible printed circuit board according to claim 1 , wherein said adhesive film comprises insulating polymer composite adhesives containing acrylic, cast polypropylene, epoxy, or polyurethane or a combination.
10. The flexible printed circuit board according to claim 9 , wherein said insulating polymer composite adhesive has a dielectric constant less than 3 at a frequency of 10 GHz.
11. The flexible printed circuit board according to claim 9 , wherein said insulating polymer composite adhesive comprises a thermosetting adhesive having a curing temperature between about 150 and 200° C. and a peeling strength of no less than 1 N/mm with respect to said top and bottom metal layers and said top and bottom base film.
12. A method of fabricating a self-powered flexible circuit board package comprising:
providing a flexible printed circuit board with a printed lithium ion battery according to claim 1 ; and
mounting a plurality of active and passive electronic devices on top of copper traces wherein at least one of said active devices is connected to and powered by said printed lithium ion battery.
13. The method according to claim 12 wherein the said active electronic devices are integrated circuits (IC) with different functionalities including one or more of: RF (Radio Frequency) IC, memory chips, logic IC, converter IC, power management IC, application specific IC (ASIC), microcontroller unit (MCU), display driver IC, touch driver IC, touch and display drive integration (TDDI) IC, and biometrics sensor & controller IC.